In information processing apparatuses, storage devices for storing bit information, and arithmetic devices for performing calculation using bit information are widely applied to consumer appliances and communication devices. At present, dominant storage devices and arithmetic devices adopt logical elements such as a transistor made of a semiconductor.
In the 1950s before logical elements using today's semiconductor transistors as basic elements became the mainstream, logical elements called parametrons were extensively studied and developed in Japan. The parametron executes a logical operation by handling, as a bit, an oscillation state having one of two different phases generated when a resonator is parametrically excited (reference 1: E. Goto, “The Parametron, a Digital Computing Element which Utilizes Parametric Oscillation”, PROCEEDINGS OF THE IRE, vol. 47, pp. 1309-1316, 1959).
FIG. 10 is a circuit diagram showing the arrangement of the basic elements of a conventional parametron mentioned above. The parametron includes an input AC signal source 1001 having a frequency f, a phase inversion switch 1002, a coupling transformer 1003, a capacitor 1004, a coupling resistor 1005, an inductance 1006 having two coils, an excitation switch 1007, an excitation AC power supply 1008 which generates an excitation AC signal having a frequency 2f, and an output terminal 1009.
The main part of the parametron is formed from the capacitor 1004 and inductance 1006 and is an LC resonator having a resonance frequency f. The LC resonator is parametrically excited at the frequency f by periodically modulating the value of the inductance 1006 of the LC resonator at the frequency 2f in accordance with an excitation AC signal from the excitation AC power supply 1008. Consequently, the LC resonator produces two oscillation states different in phase by π. Either of the two oscillation states can be selected based on the phase of an input AC signal output from the input AC signal source 1001 before the start of excitation by turning on the excitation switch 1007 and applying an excitation AC signal.
In this parametron, an AC signal with the resonance frequency f output from the input AC signal source 1001 is applied before excitation, causing the LC resonator to resonate via the coupling transformer 1003. In this state, the excitation switch 1007 is turned on to start parametric excitation. Then, the phase of the input AC signal supplied from the input AC signal source 1001 is maintained. This oscillation state continues even if the input of the AC signal from the input AC signal source 1001 is withdrawn later. The phase inversion switch 1002 inverts the AC signal input from the input AC signal source 1001, exciting the LC resonator selectively in the two excitation modes different in phase by π. The LC resonator can maintain the selected excitation mode.
In calculation using parametrons, the two oscillation states stored in the LC resonator as described above are sequentially transferred to different parametrons. This can implement a shift register, AND circuit, OR circuit, NOT circuit, and the like.
Parametrons were superior in cost and performance to semiconductor elements in those days, and even practical devices were developed. However, subsequent rapid progress of semiconductor transistors forced calling off of the development of parametrons because they were inferior in speed, degree of integration, power consumption, and the like.